I just replaced my rear drums with the Right Stuff Disc Brake conversion with the parking brake. Can I stick with the old valve or should I get a disc brake proportioning valve? Hawks sells used disc brake valves.

 

Possibly. I'd just run with what you've got and feel it out first, and then decide what adjustments are needed.
This link has a table of the stock proportioning valves that were offered and how to identify them.

https://www.thirdgen.org/forums/brak...ng-torque.html

 

You can also do the stiffer spring upgrade to the drum valve. I went to disc and waited to do the upgrade. The rear brakes didn't work like I wanted them to. I did the spring upgrade and the rears work great now. Some have had no issues when changing over so you might have to just try what you have and see. The spring you will need is a Grainger 1NCR5

 

This is what I was thinking, or if you are going to spend the money anyway go with an aftermarket adjustable valve so you can dial in the balance you want.